The present invention relates to an electron beam exposure method and apparatus and, more particularly, to an electron beam exposure method and apparatus for drawing a pattern using a plurality of electron beams for the purpose of directly drawing a pattern on a wafer or exposing a mask or reticle.
In an electron beam exposure apparatus which performs exposure by irradiating an electron beam on a substrate, when the beam current is large, the electron beam image projected onto the substrate blurs due to a Coulomb effect. Most of blurring caused by the Coulomb effect can be corrected by re-adjusting the focal point position of a reduction electron optical system for projecting an electron beam, but some blurring remains uncorrected. In a variable shaping exposure apparatus which shapes the sectional shape of an electron beam within a maximum range of about 10 .mu.m.sup.2, the blurring produced by the Coulomb effect is predicted from the area of the shaped beam, and apparatus parameters (beam current density, half beam incident angle, beam acceleration voltage, and optical length of the reduction electron optical system), and the focal point of the reduction electron optical system is adjusted in accordance with the prediction result.
In a multi-electron beam exposure apparatus which irradiates an array of a plurality of electron beams in line onto a substrate, deflects these electron beams to scan the substrate, and draws a pattern by individually ON/OFF-controlling the electron beams to be irradiated in correspondence with the pattern to be drawn, since the electron beams are dispersed, i.e., since the effective current density per unit area on the substrate is low, blurring due to the Coulomb effect is small. This means that when the blurring due to the Coulomb effect is confined within a predetermined value, the multi-electron beam exposure apparatus can improve the exposure throughput by applying larger beam currents than the variable shaping exposure apparatus.
In order to confine the blurring due to the Coulomb effect within the predetermined value, in the multi-electron beam exposure apparatus, the current density of each electron beam is limited under the assumption that all the electron beams are irradiated onto the wafer. However, in the multi-electron beam exposure apparatus, since a plurality of electron beams draw different patterns, all the electron beams are rarely irradiated onto the wafer at the same time.